Solutions to Global Energy Problems May Exist in the World’s Smallest Materials

Associate Professor Yi Zheng, mechanical and industrial engineering, is examining some of the world’s biggest problems—such as climate change and dependency on fossil fuels—and finding solutions in the world’s smallest materials. His research focuses on nanomaterials, which generally range in size from 1 to 100 nanometers (a nanometer is one billionth of a meter).

Recently, Zheng has been awarded a $500K prestigious CAREER Award from the National Science Foundation to create new fundamental knowledge about nanoscale radiative heat transfer, which is needed to solve pressing problems in energy harnessing, conversion, and cooling. The project aims to design nanomaterials that can be integrated into solar cells to increase their effectiveness and make solar energy a more appealing and viable prospect against other forms of power. In addition, it will explore radiative cooling, a process by which energy from the sun is harnessed to lower temperatures.

While the general public is aware of the sun’s ability to generate heat, it’s not yet a mainstream idea that it can also be used to cool things down. “When people talk about cooling, all they know is water-based cooling, where you have water circulating to reduce temperatures,” says Zheng. “But this radiative cooling material I’m working on could replace traditional air conditioning units.”

Traditional ACs use an immense amount of electricity to provide their users with cooler temperatures— and using electricity causes greenhouse gases to enter the atmosphere. By contrast, the radiative cooling technology Zheng is working on cools things down without using nearly as much energy, reducing the carbon footprint of temperature regulation.

Zheng knows that solving global energy difficulties needs to be a collaborative effort. “What I’m doing is just a small piece of the puzzle,” he says. To that end, his project also intends to foster young people’s interest in the potential of nanomaterials, paving the way for future engineers to work toward solving these problems. “I want to show the public how cool nanomaterials are, especially high school students,” Zheng says. “I want to bring them into nanoengineering, where they can come up with their own solutions to these problems.”

The fascinating nature of nanoengineered materials has opened the door to novel approaches for conducting research in the field of nanoscale energy conversion and cooling technology. This project creates new fundamental knowledge about nanoscale radiative heat transfer, needed to solve pressing problems in energy harnessing, conversion and cooling. The ability to manipulate, suppress and tune the radiative properties of nanoscale objects becomes essential in diverse areas like solar and thermophotovoltaic energy conversion, waste heat recovery, and potential energy savings by radiative cooling. The characterization of low-cost, highly effective thermal nanomaterials is necessary for basic scientific thermal research and industrial production. Given the potential of these technologies, there is a need to attract talent and generate interest in young minds. The project establishes, supports, and nurtures an environment that encourages nanoengineering entrepreneurship and leadership and exposes high school students to small scale heat transfer technologies to get hands-on experience about nanomaterials and solve real-world societal and global energy challenges. Hands-on NanoEngineering workshops are to be conducted in partnership with local high schools to increase the quantity and quality of students, especially minorities and women.

This project aims to conduct a comprehensive study relevant to nanoscale radiative thermal transport due to photonic metamaterials in both far-field and near-field regimes. The objective of this project is to better understand the physics of radiative thermal transport at the nanometer scale, focusing mainly on thermal, optical and unique combinations of these properties of nanostructured materials. It includes three research tasks: (1) explore novel nanomaterials using computational methods and advanced spectroscopy techniques, (2) manipulate thermal radiative wavelength selectivity in near-field and far-field regimes, and (3) demonstrate photonic metamaterials-based thermophotovoltaic energy conversion and radiative cooling. The knowledge gap will be closed between nanoscale thermal transport and radiative wavelength selectivity which attributes to the enhanced thermal infrared energy harvesting, conversion, and photon-based cooling, both necessitate exploring interdisciplinary engineering discoveries and approaches when these technologies in the areas of thermal transport processes and nanoengineering are combined to function as an integrative energy system.